Sucrose Electrochemical Reduction Of The Synthesis Of Mannitol And Sorbitol

D-mannitol and D-sorbitol have recently come into wide use as the materials for medicines, foodstuffs and chemical products, etc. particularly with the applied realm of mannitol being broadened, the demanding of it is increasing year by year. The price of mannitol is higher than it of sorbitol. Now, in our country the sorbitol is produced by catalytic hydrogenation of glucose and the formation ratio of sorbitol is more than 90%. Recently, the producing of mannitol is main to withdraw from kelp in the factories of beach cities, such as Qingdao, Dalian, etc. And because of suffering the limit of nature resources, the cost is high. Therefore, synthesis of mannitol is suffering people to pay attention to. Now, in some factories they use the method of simultaneous hydrolysis and catalytic hydrogenation sucrose aqueous solution. It is well known that a mixture of sorbitol and mannitol in aqueous solution can be produced by catalytic hydrogenation of invert sugar but the yield of mannitol can not exceed 25 percent by weight, based on total dry solids. And the method asks for high pressure, high temperature and catalyst. Requestments of equipment is high and the products refine is difficult. The elective organic synthesis can be done at normal pressure and temperature and need' t special reagent.Our experiment is to adopt the electrochemical method. In order to increase the formationrate of mannitol, we choose sucrose as ,attrial, electroreduce the mixture of glucose fructose hydrolyzed from sucrose and mannose isomeizated front glucose by ammonium molybdate. To now, we know this lesson has not been reported through investigation of documents, so the study valuable. The major contedts of the lesson are described as followed:(l)The factors effected hydrolysis of sucrose such as pH, temperature, consistency, time were researched and the optimum operating parameters were obtained. At optimum conditions pH=3, 100℃, 2.5 hours and hydrolysis time 2 hours, the conversion ratio of hydrolysis was about 97%.(2) Invested the affect of ammonium molybdate to conversion ratio of is isomerization when PH=3, 100℃, 2.5 hours and the percent by weight of glucose is 25%. We use ultraviolet spectrometry to estimate mannose. The result is the weigh of ammonium molybdate is 0.3 percent of glucose. Mannose' s yield can be about 35%.(3) We solved the problem that Ni easily shed from the electrode after electroplate and can' t be used for a long time. Using Ni electrode and Raney Ni powder replace the Raney Ni electrode. Factors influencing the convertation rate of sugars were current density, initial concentration of sugars, pH, temperature and passed charge. Thu optimumconditions were determined. Current density was 3. OA/dm², initial concentration of sugars was 0.5mol/l, pH was 9, temperature was 35 ℃ , passed charge was 1.3F/mol. At the optimum conditions the convertation rate was 83%, the mannitol formation ratio is 31% which was high than before(20%).(4) Decolorized electrolyte with a little amount - of active carbon to give a colorless solution. And took off the salt (Na₂SO₄ using C₂H₅OH. Concentrated and crystallized and obtained the solid mannitol and sorbitol aqueous solution. The retrieve rate is 86%, purity of mannitol estimated with gas chromatography is 81.6%.Using electrochemical method and replaced Raney Ni electrode with Raney Ni powder we improved the formation ratio of mannitol and sorbitol. Now, this lesson has not been reported internal and external. There need to research the other isomerizer to improve mannitol' s formation ratio...